Activation of Mg-Hg anodes by Ga in NaCl solution

The electrochemical and corrosion behaviors of Mg-5Hg-XGa alloys (X=0, 1, 5 and 22 at.%) in 3.5wt.% NaCl solution were studied by direct current (dc) and alternate current (ac) measurements under different polarization conditions. Scanning electron microscopy (SEM), energy spectrum analysis (ESA) and X-ray diffraction (XRD) were employed to characterize the microstructure and phase composition of the above alloys. Intermetallic compounds Mg(3)Hg, Mg(21) Ga(5)Hg(3) and Mg(5)Ga(2) were formed with the additions of 1, 5 and 22 at.% Ga into Mg-5Hg alloy. Attention was paid to the influence of Ga on electrochemical properties and microstructure. The best electrochemical activity occurs in Mg-5Hg-1Ga alloy, with an open circle potential of -2.124 V and a mean potential of -1.992 V. The best corrosion resistance of the Mg alloys occurs in Mg-5Hg-5Ga alloy, with a corrosion current density of 0.42 mA cm(-2). Activation mechanism of Mg-Hg-Ga alloy is dissolution-deposition of Hg and Ga atoms. (C) 2008 Elsevier B.V. All rights reserved.